1. Field of the Invention
The present invention relates to an ion concentration measuring electrode that is capable of being used to measure pH and various ions and a method of manufacturing an ion concentration measuring electrode, and more particularly, to a low impedance ion concentration measuring electrode that can be readily adapted for flow-through measurements.
2. Description of Related Art
The prior art is aware of numerous different procedures and apparatus for measurement of pH and ion concentrations. This technical field has been very active for a considerable period of time and both laboratory and industrial instruments have been successfully utilized. As an illustrative example, FIG. 5 discloses a schematic of a pH meter that comprises a glass electrode a (ion concentration measuring electrode) and a reference electrode b. A glass internal electrode c is mounted within a housing and emerged in a glass electrode internal solution d. The tip of the housing is an electrode response section e. A reference electrode internal electrode f is mounted in the housing of the reference electrode b and it also contains a reference electrode internal solution h. At the tip of the housing is a liquid junction i. A comparison of the outputs of the respective electrodes a and b provide a voltage reading indicative of the pH measurement.
The electrode response section e can be made of a spherical thin film glass in the range of thickness of 100 to 150 microns. Since the surface area which provides the liquid contact is relatively small and narrow, a very large impedance (usually in the range of 100 Mohms) is experienced. Therefore, a high input insulated circuit of 10.sup.12 ohms, or more, is usually required for measuring the electromotive force, with the resulting complications in the electric circuit.
While it may be assumed that the pH response performance of such an electrode response section e could be enhanced by further reducing the thickness of the glass film, which is in contact with the liquid sample, there is a limitation in terms of strength and processing procedures, and accordingly, a practical limitation is a glass film thickness of 100 to 150 microns which makes it extremely difficult to produce thinner products that could be commercially utilized.
Thus, the prior art has experienced certain limitations as a result of the conventional designs of the electrode response sections in pH meters and various ionic measurement instruments.